Furnace sawdust burners



March 31, 1959 A. L. WALTERS 2 ,879,727

FURNACE SAWDUST BURNERS Filed June 29, 1953 ARTHUR L. WALTERS V TOR.

ATTO RNEY.

FURNACE SAWDUST BURNERS Arthur L. Walters, Boise, Idaho Application June 29, 1953, Serial No. 364,802

8 Claims. (Cl. 110-29) My invention relates in particular to means for controlling the quantity, flow and combustion of sawdust, hogged fuel and like materials as the same are fed into the burner box.

One of the primary objects of my invention is to provide suflicient means for admitting air at the desired locations in connection with the feeding of fuel into' the burner box so as to insure proper combustion and efficient operation.

Another object of my invention is to provide a fuel burner of the character described which is simple in construction and which may also be cleaned and repaired with little inconvenience.

A further object of my invention is to provide a granular fuel burner which will operate successfully on all types of sawdust, including fine resaw sawdust, coarse green sawdust, or hogged fuel.

A still further object of my invention is to construct a having a main grate with a curved rear end thereby re ducing the growing tendency in the size of the grate during regular use of the burner.

A still further object of my invention is to so construct a fuel guide ring, a restrictor grate and a main grate with such a predetermined distance between the bottom of the fuel guide ring and the main grate as to control the flow of fuel on the main grate to such an area thereon as to insure against smothering the fire or causing backfiring.

With these and other incidental objects in view, my invention consists in certain novel features of construction and combination of parts the essential elements of which are hereinafter set forth.

In the drawings:

Fig. 1 is a side elevation of my improved sawdust burner with part of the fuel hopper and burner box broken away, showing the relationship between the fuel hopper, the fuel guide ring, the restrictor grate and the main grate.

Fig. 2 is a plan view in partial section along line 2-2 of my improved sawdust burner.

Fig. 3 is a detailed plan view of the main burner grate.

Fig. 4 is a sectional view along the line 4-4 of Fig. 3.

Fig. 5 is a detailed isometric view of the restrictor grate.

Fig. 6 is a fragmentary detailed sectional elevation view on an enlarged scale showing one manner of demountably attaching the top plate to the burner box.

Referring further to the drawings:

10 is the cover for the fuel hopper, 11 refers to the hopper which is generally circular in cross section and which inserts snugly within the fuel hopper base bowl 12 by means of friction alone. The fuel hopper base bowl is held in place by means of four stud bolts 13 and nuts 13a. These stud bolts terminate in the top plate 14 of the burner box 15 and also pass through holes in flange lugs of the fuel guide ring 16-17 thereby securing the fuel hopper base bowl and the fuel guide ring to the top plate 14 of the burner box 15. The cover 10, the fuel hopper 11, the fuel hopper base bowl 12 and the fuel guide ring 16-17 are all circular in cross-section. The

nited States Patn 'ice fuel guide ring 16-17 is made in two semi-circular parts. The back part 17 is much thicker than the front part 16 as the back part is the one subjected to the greatest heat.

A restrictor grate 18 is hingedly and removably attached to the lower edge at the front of the fuel guide ring 1617 by means of a pin 19 passing through a clevis 20 and a hole in the lower front portion of the fuel guide ring 1617, said hole not being shown in the drawings. The clevis passes through one of a series of slots 21 in the restrictor grade 18.

This arrangement enables one to raise the restrictor grate by swinging the same upward on its clevis connection with the fuel guide ring and readily clean off the surface of the main grate by removing any clinkers, stones, etc. which may be upon the main grate.

The lower rear edge of the restrictor grate 18 is provided with supporting projections 22 which rest upon the upper surface of the main grate 23 below the opening in the fuel guide ring 16-17 slightly to the rear of the center of said opening. Cleaning of the grate 23 as well as the adjusting of the same is accomplished through the burner box door 24in the front of the burner box.

The restrictor grate 18 is provided with air slots 25,

rearward inclined portion 29, the top 30 and the down ward and rearward inclined portion 31 and continuing downward in a vertical solid portion 32 to the floor of the burner box. The top portion 30 of this shoulder is provided with a plurality of holes 33. These holes have a diameter but slightly less than the width of the top surface 30. This construction makes it impossible for ashes to accumulate on the shoulder and insures the free passage of air through the holes 33 even if the granular fuel spreads upon the main grate to the inclined portion 29 of the curved shoulder. Any ashes which would not slide off the inclined forward and rear portions of the curved shoulder would fall through the holes 33.

The restrictor grate is designed to limit the area in the front portion of the main grate to be covered with granular fuel and the distance between the base of the granular fuel on the surface of the main grate and the shoulder at the rear thereof may be adjusted by moving the main grate either forward or backward on the floor of the burner box.

In my burner there is no restricting means such as a controlled throat between the fuel supply hopper and the main grate. Any such attempted regulating means tends to clog the fuel supply within the throat. In my burner the fuel supply is permitted to flow down freely by gravity upon the main grate. It has been found that the angle formed by ordinary sawdust flowing thus freely upon the main grate is about 45 off perpendicular and that a distance of not less than three inches should be maintained on the main grate between the shoulder at the rear end of said grate and the base of the sawdust on the grate for the free passage of air through the air slots 27. In case of any maladjustment of the main grate for the character of the fuel used which might cause the base of the fuel supply on the main grate to reach the shoulder at the rear end of. the grate there would still be no,

aware? in Q By adjustment of the restricter grate through selecting the proper slot 21 in attaching the same to the lower edge of the fuel guide ring the quantity of fuel flowing upon the main grate may be controlled and at the time of such adjustment the main grate 23 may be moved forward or backward just the right distance to provide the proper coverage of the surface of the main grate so as to leave a space for flow of air through the slots 27 between the base of the fuel on the grate and the base of the raised shoulder. If this distance is less than three inches horizontally between the perimeter of the fuel guide ring and the base of the raised shoulder on the main grate it might be found that the required amount of air flow would need to be supplied through the holes 33 of the shoulder. However, thissupply would be sufficient to avoid smothering, of the tire or causing back firing.

The the box is provided with an outlet 151 which communicates with the interior of a furnace or heat, exchanger (not shown in the drawings) for the passage of gases of combustion to the furnace or heat exchanger inthe direction indicated by arrows. The entire inside of the firebox 15 is lined with firebrick 15b. Referring to Fig. 1 the left hand side is considered as the front of the sawdust burner.

The burner box 15 may have a floor constructed as a part of the burner box, but in most cases the foundation (such as the cement floor upon which the burner and {)urnace are installed) furnishes the floor for the burner The curved back of the main grate with its curved shoulder is such as to avoid extensive width growing of the grate during its subjection to the extreme heat produced during operation of the burner. This construction has made it possible to construct the main grate with a clearance of not over one-fourth of an inch between the grate and the the box lining.

The back part of the grate is the portion which is subjected to the most heat. The holes 33 in the raised portion not only prevent smothering and back-firing but also serve to keep the back end of the grate from becoming too hot. This adds materially to the life of the grate.

Having thus described my invention I claim:

1. In a. granular fuel burner: a burner box having an outlet at the rear of said burner box adapted to open into or communicate with the interior of, selectively, a furnace or other heat exchanger; a fuel hopper communicating with the interior of the burner box and supported by said burner box; a main grate provided with slots and supported by and slideably mounted upon the floor of the burner box; a fuel guide ring of circular cross section extending belowthe opening of the hopper downwardly from the top of the burner box to a point not more than three and. one-half inches above the top surface of the main grate; said main grate being slideable from front to back within the burner box, below the fuel guide ring, and having a raised portion at the back edge thereof provided with air holes and arching substantially concentric with and a predetermined distance beyond the fuel guide ring; and a restrictor grate provided with air slots and fingers adjustably and hingedly attached to the lower front edge of the fuel guide ring sloping downwardly to the rear and having its lower edge supported by the main grate at a point below and slightly to the rear of the center of the opening in the fuel guide ring.

2. In a granular fuel burner: a burner box having a combustion area and an opening adapted to communicate with the interior of, selectively, a furnace or other heat exchanger; afuel hopper communicating with the interior of the burner box, the lower portion of the fuel hopper is of circular cross section; a manually horizontally adjustablemain grate-mounted upon the floor of the burner box below the fuel hopper, having a flat vaporizin surface containing a plurality of air slots and having a raised arc-like portion at the rear of said grate containing a plurality of air holes in the top of said raised portion;

below the fuel hopper and communicating therewith, a fuel guide ring of circular cross section divided into two semi-circular parts extending from the bottom of the fuel hopper to a point not more than three and one-half inches above the surface of said main grate; a restrictor grate adjustably and hingediy connected to the front lower edge of the fuel guide ring, slanting downwardly to the rear from its connection with the fuel guide ring to a point of contact with the top surface of the main grate, which point is slightly beyond the center of the opening of the fuel guide ring.

3. In a granular fuel burner: a metal structure having an outlet adapted to communicate with the interior of, selectively, a furnace or other heat exchanger having sides, front, and a top plate containing a round opening; a fuel guide ring, circular in cross section converging downwardly through the hole in the top plate from top to bottom, and having a flange at its upper end resting on the top plate; securing lugs integral with said supporting flange; a hopper base bowl circular in cross section communicating through the fuel guide ring with the interior of said metal structure, the lower perimeter of said hopper base bowl having a flared flange with integral lugs correspond ing with and complementary to the lugs on the flange of the fuel guide ring; stud bolts demountably attaching the fuel guide ring and the hopper base bowl to the top plate.

4. In a granular fuel burner having an outlet adapted to communicate with the interior of, selectively, a furnace or heat exchanger and having in its structure a top demountable from its sides: a front plate and a top plate having an opening near the front thereof; a fuel guide ring of circular cross section made in two parts, communicating with the interior the burner and extending downward below the top plate through the opening therein; a main grate slideable to a position below said fuel guide rings and having a solid rear-end curved within its horizontal plane with a raised shoulder thereon and a plurality of holes in the top of said shoulder; a restrictor grade adjustable and demountably attached to the front lower edge of the fuel guide ring and having its rear portion resting upon the top surface of the main grate at a point below and slightly to the rear of the center of the opening in the fuel guide ring.

5. In a granular fuel burner: a burner box having an outlet adapted to communicate with the interior of, selectively, a furnace or other heat exchanger; a top plate, having a hole therethrough, on said burner box; a fuel hopper base bowl of circular cross section, converging uniformly from top to bottom, supported by said top plate; a fuel hopper fitting snugly within and being supported by the fuel hopper base communicating with the interior of the burner box; a fuel guide ring of circular cross section divided into two semi-circular parts below the fuel hopper base bowl, communicating with the interior of the burner box, attached to the top plate of the burner box and extended through said hole in said top plate, said fuel guide ring and said fuel hopper base bowl being rigidly attached to the top plate of the burner box; a flange at tached to the hopper base bowl having lugs with holes therein; a flange attached to the fuel guide ring having lugs with holes therein; stud bolts passing through the holes in the lugs of the fuel hopper base bowl and the holes in the lugs of the flange to the fuel guide ring and terminating in the top plate of the burner box; a horizontally adjustable main grate within the burner box. slideable to a position under the fuel guide ring; a restrictor grate adjustably and hingeclly attached to the lower front edge of the fuel guide ring, slantin downwardly therefrom and having the rear edge supported on the horizontally adjustable main grate at a point below and slightly to the rear of the center of the fuel guide ring opening; a raised, curved shoulder portion at the back of the main grate, the perimeter of which is equidistant from and concentric with the curvature of the fuel guide ring, said curved shoulder having a plurality of holes in its top portion.

6. In a granular fuel burner: a burner box having an outlet adapted to communicate with the interior of a furnace; a main grate, having slots therein and having an arcuate rear end, said grate being disposed within the burner box; a raised shoulder portion at the rear end of the grate conforming to the arcuate end of the grate, said shoulder having air holes in its top; and a fire-brick lining inside the burner box having a clearance of not in excess of one-fourth of an inch between the main grate and said fire-brick lining.

7. In a granular fuel burner: a burner box having an outlet adapted to communicate with the interior of a furnace; a main grate disposed within the burner box, said grate having slots therein and having an arcuate back end; a raised shoulder portion arching horizontally in conformity with the back of the main grate and having air holes through the top of said raised portion; a firebrick lining inside the burner box, having a clearance of not in excess of one-fourth of an inch between said firebrick lining and the main grate; a fuel guide ring of circular cross section communicating with the interior of the burner box and consisting of two semi-circular removable parts, the back section being of substantially greater thickness than the front section, the bottom of said fuel guide ring being approximately 3 inches above the top surface of the main grate, the main grate being adjusted within the burner box to a position under the fuel guide ring so that the raised portion of the main grate is to the rear and beyond the gravity flow area of fuel as it descends by gravity flow through the fuel guide ring.

8. In a granular fuel burner: a burner box having an opening therein adapted to communicate with the interior of a furnace or, selectively, other heat exchanger; a main grate within said burner box; a top plate demountably attached to said burner box, said top plate having an opening near its front end which opening is predetermined by the size of said main grate; a fuel guide ring circular in cross section, composed of two semi-circular parts converging slightly from top to bottom, having a flange around its upper perimeter resting on the top plate of the burner box, the lower portion of said fuel guide ring adapted to extend down through the opening in said top plate to within a predetermined distance of not more than three and one-half inches above the top surface of the main grate; a raised curved rear portion of the main grate, the base of which extends not less than three inches beyond the perimeter of the lower edge of the fuel guide ring, said main grate being adapted for slideable adjustment within the burner box below the fuel guide ring.

References Cited in the tile of this patent UNITED STATES PATENTS 497,559 Van Evera May 16, 1893 755,277 Coppens Mar. 22, 1904 1,641,545 McCoy Sept. 6, 1927 1,758,478 Snyder May 13, 1930 1,806,916 Requa May 26, 1931 1,818,503 Pfau Aug. 11, 1931 1,832,223 Klopfenstein Nov. 17, 1931 2,165,802 Longtin July 11, 1939 2,183,648 Johnson Dec. 19,1939 2,530,522 Harris Nov. 21, 1950 FOREIGN PATENTS 10,282 Germany July 16, 1880 503,570 Great Britain Apr. 11, 1939 

